MODES OF FEEDING 153 
descend—seeking their food along the bottom and being obliged to come to the 
surface for air. The larve of Anopheles normally remain at the surface. They 
lie with their bodies extended straight and locked to the surface film by the 
chitinous flaps surrounding the sessile breathing-tube and by the stellate tufts 
of the abdominal segments. When they move they do so in very rapid jerks, 
either along the surface, or, when alarmed, descending into the water. When the 
Anopheles larva is at rest its body is always extended in a straight line and this 
gives these larvee a curiously rigid appearance which is very characteristic. The 
head is very motile and in feeding its ventral side is usually turned upward, 
while the mouth-brushes, in constant vibration, produce a current which brings 
floating particles to the mouth. 
The larve of other mosquitoes progress through the water with a peculiar 
snake-like motion, most marked in the species with the longest bodies, such as 
Aédes calopus and Aédes triseriatus. The movement is a lashing one; the body 
is bent in the shape of a letter “S ” and lashed from side to side. Certain larve 
can also be seen, at times, progressing merely by the action of the mouth-brushes. 
In the former case the larva progresses through the water backwards, in the 
latter case it moves head foremost. _ 
The larve of many Culea and Aédes feed mostly while suspended from the 
surface film by the end of the breathing-tube, obtaining their food by the action 
of the mouth-brushes. Other larve feed at the bottom and only come to the 
surface at intervals to obtain air, this interval differing with the species. Some, 
indeed, never rise to the surface and obtain the necessary oxygen from the water 
by osmosis, or, in the case of Mansonia, from the vascular roots of aquatic plants. 
The attitude, when suspended from the surface film, differs with the species. 
Uranotenia maintains a horizontal body-position and this, together with the 
similarity in the shape of the head, produces a resemblance to Anopheles which 
has often proved deceptive. The larva of Culex territans holds its body in a 
nearly horizontal position when suspended from the surface film, but the long 
perpendicular breathing-tube and the broad deflexed head give it a characteristic 
appearance. Other species suspend themselves with their bodies at more or less 
of an angle. In certain species of Aédes the body hangs nearly straight down. 
Certain larve feed altogether at the bottom and only come to the surface at 
long intervals. Such is the case with many species of Aédes. Wycomyia and 
other sabethids are bottom feeders and are busy most of the time working over 
the rubbish at the bottom of the breeding-places ; they seem to require but little 
air and never remain suspended from the surface film for any length of time. 
The larve of certain species of Culex lie upon the bottom back downward, 
anchored, so to speak, by a pair of hooks at the tip of the breathing-tube; the 
head is somewhat deflexed and the large mouth-brushes procure the food ; they 
rise at intervals for air. Psorophora discolor has a larva of very similar habits; 
however, it never comes to the surface, procuring oxygen from the water by 
means of the highly developed anal gills. 
The predaceous larve can not be said to hunt their prey. They remain 
quiescent until a larva comes within reach when they seize it with great rapidity. 
